Pavement Quality Concrete (PQC) Pavement – M40 Grade
1.0 Scope
This methodology shall be applicable for construction of dowel jointed or plain cement concrete of M40 grade pavement in accordance with the lines, grades, camber and thickness as shown in the drawings using fixed forms.
This clause establishes applicability limits of the methodology and ensures compliance with approved drawings, levels, and pavement thickness essential for structural performance.
2.0 Materials
2.1 Cement
These shall consist of Ordinary Portland Cement of approved source. The minimum cement content shall be 350 Kg/m³ and maximum 425 Kg/m³.
Cement silos shall be moisture-tight. Batch-wise cement consumption shall be recorded to verify compliance with specified limits.
2.2 Admixtures
The admixtures shall conform to IS 6925 and IS 9103 and shall improve the workability of concrete or extension of time and they will not have any effect on the properties of concrete. The performance of these admixtures will be proved both on laboratory trials and in trial paving works. Admixtures containing calcium chloride shall not be used.
Each admixture shall be approved by Engineer-in-Charge based on compatibility tests with cement and aggregates used for the project.
2.3 Aggregates
The aggregates shall be of crushed stone or naturally available conforming to IS 383. The coarse aggregate shall be clean, hard, strong, dense and durable. The fine aggregate shall be clean natural sand or crushed stone sand or combination of both. These shall be free from clay, shale, loam, mica and other organic matter.
Aggregate stockpiles shall be segregated by size, kept on paved surfaces and protected from contamination and excessive moisture variation.
2.4 Water
Water used for mixing and curing of concrete shall be free from oil, salt, acid and other substances which are harmful to concrete.
Potable water is generally acceptable. Non-potable sources shall be tested as per IS 456 before use.
2.5 Mild steel bars for dowel and tie bars
These shall conform to the requirements of IS: 432, IS: 1139 and IS: 1786 as relevant. The dowel bars shall conform to Grade S 240 and tie bars to Grade S 415 of I.S.
Alignment, level, and embedment depth of dowel and tie bars shall be checked before concrete placement to ensure effective load transfer.
2.6 Pre-Molded joint filler
To be used for expansion joints abutting structures like bridges, culverts and at end of the day's work. Thickness 20–25 mm or as shown in drawings, complying to IS 1838. It shall be 25 mm less in depth than the thickness of slab and provided in suitable lengths not less than lane width. Holes shall be made to accommodate dowel bars.
Joint filler boards shall be stored vertically and protected from moisture to prevent warping.
2.7 Joint sealing compound
Hot poured elastomeric type as per AASHTO M282 or cold poured polysulphide type as per BS 5212-part2, having flexibility, resistance to age hardening and durability.
Proper joint sealing prevents ingress of water and incompressible materials, reducing pumping and joint deterioration.
2.8 Separation membrane
A separation membrane of impermeable plastic sheeting 125 microns thick shall be laid between the concrete slab and sub-base by nailing with concrete nails to the lower layer. Where overlap is necessary the same shall be at least 300 mm.
This membrane prevents loss of moisture from concrete and avoids bonding between PQC and underlying layers.
2.9 Concrete Strength
The concrete mix design in the laboratory, correlation between flexural and compressive strengths shall be established on the basis of at least thirty tests on samples. Quality control in the field shall be exercised on the basis of flexural strength. Materials and mix proportions shall remain substantially unaltered during daily production. Maximum free water cement ratio: 0.50.
The ratio between the 7 and 28 day strengths shall be established in advance by testing pairs of beams and cubes on at least six batches of trial mix. The average 7-day strength divided by average 28-day strength yields ratio R (to three decimals).
If any four consecutive 7-day test results fall below the required 7-day strength (derived from R), the cement content shall be increased by 5% by weight (or as agreed by the Engineer) without extra payment. Maintain the increased cement content until four corresponding 28-day strengths have been assessed. Adjust mix to maintain required workability.
Flexural strength governs rigid pavement performance as it directly reflects slab behaviour under wheel loads.
2.10 Workability
Workability requirements at batching plant and site shall be established by slump tests during trial length. Typical slump values: Slip form — 30 ± 15 mm; Fixed form — 50 ± 15 mm.
Slump variation beyond limits shall trigger immediate mix adjustment and investigation.
3.0 Construction Procedure
3.1 Mixing
Materials shall be mixed in a mechanized batching plant with air-conditioned centralized control cabin, minimum 4 bins, weigh hoppers and automatic weighing devices using calibrated load cells. Mixer shall be capable of producing a homogeneous mix without segregation. Mix timing per manufacturer's recommendations; automatic alarm/timing device recommended.
Mixing requirements align with MoRTH Clause 602.3.2 ensuring uniformity, accurate proportioning, and consistency of PQC.
3.2 Joints
The location and type of joints shall be as shown in the drawings.
3.2.1 Transverse Joints
Transverse joints shall be contraction and expansion joints constructed at the spacing described in the Drawings. They shall be straight within tolerances except at junctions/roundabouts where drawings govern.
Transverse joints control cracking due to temperature and shrinkage stresses and ensure effective load transfer.
3.2.2 Contraction Joints
Contraction joints shall be mechanical saw cut; can start as early as 6–8 hours after paving (initial hardening). Groove width 3–5 mm, depth 1/4 to 1/3 slab depth. Expansion joints shall have joint filler board and prefabricated assemblies. Dowel bars: mild steel as indicated in drawings, positioned at mid-depth within ±20 mm tolerance.
Joint cutting and dowel positioning as per MoRTH Clause 602.6.2 & 602.6.5.
3.2.3 Expansion Joints
Expansion joints shall comprise pre-moulded joint filler boards conforming to MoRTH Clause 602.2.7 and dowel bars conforming to MoRTH Clause 602.6.5, as detailed in the approved drawings. The adjacent concrete slabs shall be fully separated, and the annular space around the dowel bars shall be effectively sealed with suitable compressible material to prevent ingress of cement slurry.
Ensure filler boards are vertical and continuous across full slab depth to prevent restraint.
3.2.4 Longitudinal Joints
Longitudinal joints shall be saw cut as shown. Groove depth 1/3 slab depth. Tie bars shall be deformed steel (IS 1786), painted with bituminous paint for 75 mm at both ends and positioned within middle third of slab depth.
Tie bar requirements as per MoRTH Clause 602.6.6.
3.2.5 Construction Joints
Transverse construction joints shall be placed whenever concreting is completed for the day's work or suspended for more than 30 minutes. Provide at regular contraction joint locations using dowel bars.
Construction joints ensure structural continuity where paving operations are interrupted.
3.3 Separation Membrane
Separation membrane: impermeable plastic sheeting 125 microns thick. Lay by nailing to lower layer. Overlap at least 300 mm.
Separation membrane provisions as per MoRTH Clause 602.2.9.
3.4 Dowel Bars
Dowel bars shall be mild steel round bars conforming to MoRTH Clause 602.2.6 and shall be clean, straight, and free from oil, dirt, rust, scale, or any other deleterious material.
Check dowel alignment (horizontal & vertical) before paving to avoid joint locking.
3.5 Tie Bars
Tie bars projecting across longitudinal joints shall be protected from corrosion for 75 mm on each side with bituminous paint.
3.6 Construction by Fixed Form
Fixed forms: straight steel side forms minimum 5 mm thick, minimum 3000 mm length, depth equal to slab thickness.
Rigid fixed forms ensure correct slab thickness, alignment, and edge integrity.
4.0 Trial Length
A trial length of 60 m shall be constructed full width and rolled, involving at least one transverse construction joint between hardened and fresh concrete.
Trial length requirements as per MoRTH Clause 602.3.5.
5.0 Safety Requirements
- All concrete transit mixers shall be provided with reverse horns.
- Flagman shall be provided at all exit points of the trucks / tippers.
- The speed of vehicles plying in the work area shall be restricted to 40 km/h maximum.
- If night work is carried out the area shall be provided with sufficient lighting.
- Check working condition of safety valves of air compressors.
- The 1000 mm work area on both sides shall be kept clear of unauthorized persons.
Safety provisions align with MoRTH Section 100 & IRC:SP:55.
6.0 Inspection & Test Plan (ITP)
| Activity | Inspection | Test | Frequency | MoRTH Clause |
|---|---|---|---|---|
| Material approval | Yes | Cement, aggregates tests | As per spec | 602.2 |
| Batching & mixing | Yes | Slump test | Each batch | 602.3 |
| Dowel bar placement | Yes | Alignment check | Each joint | 602.6.5 |
| Concrete strength | Yes | Flexural / cube test | As specified | 602.4 |
| Surface texture | Yes | Sand patch test | As specified | 602.11 |
